1. Field of the Invention
The present invention relates to a focus adjustment unit and a focus adjustment method, and in more detail relates to a focus adjustment unit, having a photographing lens including a focus lens, with image data being formed by receiving light of a pupil divided subject image by means of this photographing lens, for carrying out focus adjustment based on this image data, and to a focus adjustment method.
2. Description of the Related Art
A phase difference AF focus adjustment unit that carries out correlation calculation using image data that has been created by receiving light of a pupil divided subject image by means of a photographing lens, obtains a phase difference and drives to a focus, is known. With this phase difference AF method, in a case where there is a periodic pattern in the subject image a plurality of focus candidate points will be calculated, and as a result it is difficult to obtain a true focus target position.
To such an end, in Japanese Patent laid-open No. 2011-150179 (hereafter referred to as Patent literature 1), contrast evaluation values for a current position and close to that position are acquired, a focus direction is determined from a relationship between these contrast evaluation values, a contrast evaluation value for a current lens position and a contrast evaluation value for a nearby position after defocus drive by a specified amount from that position, are acquired, and focus direction is determined from these contrast evaluation values.